Wafers used in manufacturing semiconductor devices are highly accurate products. Therefore, care should be taken to protect the wafers from contaminants or shocks during storage or transportation thereof. In general, wafers are put into a container (called “front opening unified pod” or “FOUP”) when they are stored or transported.
Referring to FIG. 1, a conventional container for storage and transportation of wafers (hereinafter referred to as “wafer container”) includes a container body 1 and a container cover 3. The container body 1 is provided with a storage room 1a for storing a plurality of wafers W in a spaced-apart relationship. The container cover 3 closes and seals the opening 1b of the storage room 1a, thereby preventing foreign materials from entering the storage room 1a. This protects the wafers W stored within the storage room 1a. 
The wafer container stores highly accurate wafers and therefore needs to be kept at a high degree of cleanness. In order to keep the wafer container at a high degree of cleanness, it is necessary to periodically clean the wafer container. The cleaning operation of the wafer container is conducted by a cleaning device.
One example of wafer container cleaning devices is disclosed in U.S. Pat. No. 6,797,076. This cleaning device includes an enclosure, a rotor rotatably installed within the enclosure, a plurality of container holders arranged around the rotor to support wafer containers and a sprayer nozzle for spraying a cleaning solution to the wafer container supported on the container holders.
In operation, the wafer containers to be cleaned are held on the container holders, after which the cleaning device is turned on. Then, the cleaning device cleans the inner and outer surfaces of the wafer containers while spraying the cleaning solution from the sprayer nozzle. At this time, the rotor carrying the wafer containers makes rotation so that the cleaning solution can be uniformly sprayed on the inner and outer surfaces of the wafer containers rotating together with the rotor. This increases the cleaning efficiency of the wafer containers.
However, the conventional cleaning device has a drawback in that it is quite inconvenient to attach the wafer containers to the container holders. This prolongs the time required in cleaning the wafer containers and consequently reduces the cleaning efficiency of the wafer containers.
More specifically, when the wafer containers are attached to the container holders in the conventional cleaning device, there is a need to perform a cumbersome task of bringing the upper end portions of the wafer containers into engagement with the upper hooks of the container holders and then having the lower end portions of the wafer containers engaged with the lower hooks of the container holders one by one.
This requires a lot of time in attaching the wafer containers to the container holders and prolongs the cleaning time of the wafer containers. The prolonged cleaning time results in sharp reduction in the cleaning efficiency of the wafer containers.
In addition, the conventional cleaning device has a structure capable of cleaning only the container body but not the container cover. This further prolongs the cleaning time of the wafer containers. The prolonged cleaning time results in sharp reduction in the cleaning efficiency of the wafer containers.
Moreover, the conventional cleaning device is incapable of simultaneously cleaning the interior and exterior of the container body. Thus, there is a need to first clean the exterior of the container body and then clean the interior thereof. This further prolongs the cleaning time of the wafer containers.